Last night I found this thread under the Mavic Air by NickelPlate and found it very interesting, so I have pinched it and put it here, because I feel it would be of interest to Mavic 2 Pro and zoom as well ho uses these batteries.

No way I will be able to replace the inside cells, so I better stock up while I can get them before the next gen Mavic 3 comes out. I just have to make sure the batteries I buy will be manufactured preferable this year 2021, so that they will last a few years more. As the serial number is outside the box and I can see the box before I buy it or the seller tells me the Nr, I can check it here when it is manufactured. http://tools.retroroms.info/  
Many thanks again for this info NickelPlate.

Hello there kyalami. Good day and thank you for sharing this video with us here at DJI Forum. Just a reminder that DJI does not recommend to our fellow pilots not to do this process or modify you DJI drones intelligent flight batteries for safety and reliability purposes. Thank you.

I dont think this guy has ever seen what happens if you puncture a lipo battery or he would be using a knife.

Interesting to see!

DAFlys Posted at 9-23 04:08
I dont think this guy has ever seen what happens if you puncture a lipo battery or he would be using a knife.

Hi Da, I think hi did say somewhere in the video that you should be very careful not to puncture the bag.
It is quite clear that you should not attempt to do this yourself and also that he vas unable to find replacement battery bags. But t was interesting to see how it looked inside the battery and how difficult it was to open it. So we have to treat the battery like a little baby........

Montfrooij Posted at 9-23 05:11
Interesting to see!

Hi Peter, yes it was interesting to see how the battery was manufactured and what it looked like inside. I think it would be virtually impossible for a ordinary person to do the spot welding, which was made there for great connectivity, even if you could get replacement battery bags.

DJI Stephen Posted at 9-23 01:49
Hello there kyalami. Good day and thank you for sharing this video with us here at DJI Forum. Just a reminder that DJI does not recommend to our fellow pilots not to do this process or modify you DJI drones intelligent flight batteries for safety and reliability purposes. Thank you.

Thanks for your reply Stephen. I do not think that you have to worry about that anyone will trying to open the batteries. It is just to dangerous and it really serves no purpose to do that

One thing I'll add is that Lipo cells are the most chemically stable at a voltage of about 3.8V per cell and that is the best way to store them. You can definitely prolong the life of them by keeping them in this state when not in use. I've had lipos in my other RC models that are 3 and even 4 years old and are still going strong at 80%+ of their original capacity with no swelling because when I'm done with them I put them in storage mode. I personally don't leave my MM2 batts fully charged for any longer than a couple of days. Usually after every flight when I get home I'll either charge or discharge them to about half their capacity which is pretty close to 3.8V. You can also connect the DJI batteries to the drone and turn it on and view the individual cell voltages in the app if you want to be really specific. Fly it a little if they are charged too much.

What would be nice is if DJI were able to add a storage feature to their chargers that would balance all of the cells to 3.8V. I know the batteries discharge themselves automatically but it takes too long (9 days?) IMO to rely on all of the time. Chargers for the RC hobby have had storage charge modes for years now.

NickelPlate Posted at 9-23 09:04
One thing I'll add is that Lipo cells are the most chemically stable at a voltage of about 3.8V per cell and that is the best way to store them. You can definitely prolong the life of them by keeping them in this state when not in use. I've had lipos in my other RC models that are 3 and even 4 years old and are still going strong at 80%+ of their original capacity with no swelling because when I'm done with them I put them in storage mode. I personally don't leave my MM2 batts fully charged for any longer than a couple of days. Usually after every flight when I get home I'll either charge or discharge them to about half their capacity which is pretty close to 3.8V. You can also connect the DJI batteries to the drone and turn it on and view the individual cell voltages in the app if you want to be really specific. Fly it a little if they are charged too much.

What would be nice is if DJI were able to add a storage feature to their chargers that would balance all of the cells to 3.8V. I know the batteries discharge themselves automatically but it takes too long (9 days?) IMO to rely on all of the time. Chargers for the RC hobby have had storage charge modes for years now.

Hi NickelPlate, Thanks for your reply and further information about storage voltage of the batteries. Also great to here that you have managed to keep the batteries so good over so many years. That makes me more comfortable with the battery life. After a flight I let them cool down over night and next morning I charged them up to about 60%. I will now check in the drone what the voltage is at that percentage. I only charge the batteries that day when I am about to fly, so they never sit more than a few hours at full charge. DJI has now made it so in the firmware that I can select 2 days before they start to discharge, so they never sit too long at full charge. This is for the intelligent fly batteries for Mavic 2 Pro and the Fly Go 4 app. But I never let that happen in any case. They are just too expensive not to look after to the very best. Particularly now when they start to get difficult to get hold of. Again appreciate you reply and further comments. Thanks very much. Tony

kyalami Posted at 9-23 08:26
Hi Da, I think hi did say somewhere in the video that you should be very careful not to puncture the bag.
It is quite clear that you should not attempt to do this yourself and also that he vas unable to find replacement battery bags. But t was interesting to see how it looked inside the battery and how difficult it was to open it. So we have to treat the battery like a little baby........

He did say that as he was poking a sharp knife in there.   With all the horror stories about out batteries it does concern me,  as well as the history of dji not keeping them available for other drones.

kyalami Posted at 9-23 08:30
Hi Peter, yes it was interesting to see how the battery was manufactured and what it looked like inside. I think it would be virtually impossible for a ordinary person to do the spot welding, which was made there for great connectivity, even if you could get replacement battery bags.

Indeed!

kyalami Posted at 9-23 08:34
Thanks for your reply Stephen. I do not think that you have to worry about that anyone will trying to open the batteries. It is just to dangerous and it really serves no purpose to do that

Hi there kyalami. Thank you for the reply and for these information that you have given. Have a safe and a happy flying always.